The story flashes back to the point two days before, when Smaug smashed in the door of the Mountain in a range. The men of Lake-town saw the flashes produced by Smaug's destruction and at first thought it was the King under the Mountain and his gold. Alerted, they were therefore prepared for something and foiled the dragon's first attempts to attack Lake-town. But Smaug continued to assault the town and eventually set fire to it, destroying everything. Those who survived tried to escape by getting into the water. One of the archers defending the town, Bard, a descendant of Girion, holds out against Smaug with his arrows. Taking advice from a thrush, he shoots Smaug in his soft spot — the place near his left breast that Bilbo had spied some time before. Victorious, Bard is declared king but the Master of Lake-town objects and reminds his people of the problem of the dwarves. Birds carry the news of the death of Smaug. The Elvenking comes to the aid of Lake-town and marches north to the Mountain, eleven days after the devastation caused by Smaug.
This account of the destruction of Lake-town, the town of men, emphasizes the formidable power of Smaug, against whom even human beings are powerless. Bard appears for the first time and successfully kills the dragon by shooting an arrow into the same weak spot under his left breast that Bilbo observed earlier. It is interesting that Bard receives advice on this matter from a thrush; a thrush was the creature that reminded Bilbo of Durin's Day and allowed the dwarves to unlock the secret opening to Smaug's lair.
There is the suggestion here of the groups that will converge in the Battle of Five Armies, as the Master of Lake-town reminds his people of their enemies, the dwarves, and the Elvenking enters Lake-town to aid in the recovery from Smaug's devastation.
foiled spoiled a plan, prevented a plan from being successfully enacted.